The present invention relates generally to geographic databases and, more particularly, the present invention relates to a way to represent the altitudinal component of road geometry in a geographic database and a method for forming the representation.
Geographic databases have many uses. Geographic databases are used in navigation systems to display maps and provide route calculation and guidance. Geographic databases are also used by Internet sites to provide navigation-related features and services.
In many conventional geographic databases, a linearly extending geographic feature, such as a road, a river, or a state or municipal boundary, is represented using a series of discrete points. For example, in the case of roads, each road segment is represented by two nodes that represent the end points of the road segment, and optionally by one or more shape points that represent points along the road segment between the two nodes. Data that define each of these points (e.g., latitude, longitude, and altitude) are stored in a geographic database to represent this road segment.
Although this way of representing roads and other linearly extending geographic features works well for many applications, there is room for improvement. One area in which there exists a need for improvement relates to the representation of altitude (or altitude changes) along a road. A large number of shape points may be needed to accurately represent the actual shape of the road that has many vertical changes. Storing large numbers of shape points increases the overall size of the geographic database thereby increasing the cost of the data storage medium. Increasing the overall size of the geographic database may also require that systems that use the geographic database have faster and more powerful processors or more memory.
Accordingly, there is a need for a space efficient model for representing and storing altitude information relating to roads.